Modal verbs (and other verbs) to express OBLIGATION
Hello Everyone! Today we are looking at the verbs used to express obligation.
Must, should and ought to are the modal verbs used to express obligation. Ought to has exactly the same meaning as should but is not commonly used. Have to, which is a full verb, is also used to talk about obligation. Examples of statements, questions and negatives:-
- Tom must help Kathy.
- Must Tom help Kathy?
- Tom mustnโt help Kathy.
- Tom should help Kathy.
- Should Tom help Kathy?
- Tom shouldnโt help Kathy.
- Tom has to help Kathy.
- Does Tom have to help Kathy?
- Tom doesnโt have to help Kathy.
Must and have to are both used to talk about STRONG obligation.
Must is used when the speaker uses his/her authority and cares about the obligation being spoken about.
Example
Mother: โEmma, you must do your homework!โ Emmaโs mother is using her authority as Emmaโs parent and wants her to do her homework. It is 100% important that Emma should do her homework.
Have to is used to express general obligation. The speaker has no authority over the person being spoken to.
Example
Friend: “Emma, you have to do your homework!” Emma’s friend has no authority over her, she can’t make her do her homework but, still, the obligation is 100% strong. Have to is often used to talk about rules or laws. E.g. In India, you have to drive on the left.
Must doesn’t have a past form, so the past of must and have to is had to. You can’t show if the speaker used his/her authority or if the obligation was general.
Example
He must do his homework. (Present)
He had to do his homework. (Past)
He has to do his homework. (Present) He had to do his homework. (Past)
Mustnโt and donโt have to have completely different meanings in the negative.
Mustnโt means forbidden and donโt have to means no obligation but you can if you want to.
Example 1.
โYou mustnโt play with fire!โ You are forbidden from doing this โ You could get burnt. You wouldnโt say โYou donโt have to play with fireโ because that would mean that you can if you want to!
Example 2.
โYou donโt have to help me with the cookingโ There is no obligation but you can if you want to. (I may like some help). โYou mustnโt help me with the cookingโ means I forbid you from helping me. I really donโt want your help!
The past of donโt have to is didnโt have to. It has exactly the same meaning as donโt have to but in the past, i.e. there was no obligation but you could if you wanted to. E.g. When I was young I didnโt have to help my mother with the cooking but, if I finished my homework early, I sometimes did.
The past of mustnโt is wasnโt allowed to which means was forbidden fromโฆ E.g. โWhen I was young I wasnโt allowed to play with fireโ means โWhen I was young I was forbidden from playing with fire.โ
Should is used for mild obligation and advice.
Example
โYou should do your homework.โ It is the right thing to do and I advise you to do it.
The negative of should is shouldnโt as;
โYou shouldnโt go to bed too late.โ I advise you not to.
The past of should is should have. It means you didnโt do something but it would have been the right thing to do.
Example
โYou should have learned for the testโ โ unfortunately, you didnโt.
Shouldnโt have means that you did something but it was the wrong thing to do.
Example
โYou shouldnโt have eaten all the pizzaโ โ you did and it was the wrong thing to do!
To test your understanding of verbs of obligation, try grammar quiz as follows:
Grammar Quiz
See how much you understand about using verbs of obligation! Circle the correct sentence, A or B.
1.
A. Does he have to come to the meeting?
B. Has he to come to the meeting?
2.
A. You mustnโt drink poison!
B. You donโt have to drink poison!
3.
A. You donโt have to come shopping with me but you can if you want to.
B. You mustnโt come shopping with me but you can if you want to.
4.
A. Doctor โYou have to take this medicine three times a day for a week.โ
B. Doctor โYou must take this medicine three times a day for a week.โ
5.
A. Friend โYou must pay your school fees!โ
B. Friend โYou have to pay your school fees!โ
6.
A. When I was young I must help my mother clean our house.
B. When I was young I had to help my mother clean our house.
7.
A. Jim failed the exam! He should have studied harder!
B. Jim failed the exam! He had to study harder!
8.
A. Anna didnโt has to buy me a present!
B. Anna didnโt have to buy me a present!
9.
A. In India most school children must wear a uniform.
B. In India most school children have to wear a uniform.
10.
A. You mustnโt drive over the speed limit!
B. You donโt have to drive over the speed limit!
Answers: 1A, 2A, 3A, 4B, 5B, 6B, 7A, 8B, 9B, 10A
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